Message-ID: <2b9ecca4-4a92-44e0-f85e-2877dd08013a@gmail.com>
Date:   Sun, 17 Feb 2019 15:20:48 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Frank Wunderlich <frank-w@...lic-files.de>, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>
Subject: Re: [BUG] [FIX] net: dsa: oops in br_vlan_enabled



On 2/17/2019 9:13 AM, Florian Fainelli wrote:
> Hi Frank,
> 
> On 2/16/2019 8:22 AM, Frank Wunderlich wrote:
>> Hi,
>>
>> i've found an oops in 4.19.23/10, seems to be fixed anyhow in 5.0 (also works in 4.14.101)
>>
>> root@...-r2:~# ip link add link lan0 name lan0.5 type vlan id 5
>> root@...-r2:~# ip addr add 192.168.5.200/24 brd 192.168.5.255 dev lan0.5
>> root@...-r2:~# ip link set dev lan0 up
>> root@...-r2:~# ip link set dev lan0.5 up
> 
> So that these steps don't involve a bridge, and because we don't (yet)
> implment ndo_vlan_rx_{add,kill}_vid() netdevice_ops, there is no VLAN
> programming, it's all software
> 
>>
>> 12: lan0.5@...0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state LOWERLAYERDOWN group default qlen 1000
>>     link/ether 02:02:02:02:02:02 brd ff:ff:ff:ff:ff:ff
>>     inet 192.168.5.200/24 brd 192.168.5.255 scope global lan0.5
>>        valid_lft forever preferred_lft forever
>>
>> root@...-r2:~# brctl addbr bridge_name
>> root@...-r2:~# brctl addif bridge_name lan0.5
> 
> Unless you changed the bridge to have VLAN filtering/awareness with:
> 
> echo 1 > /sys/class/net/bridge_name/bridge/vlan_filtering
> 
> There will be no VLAN configuration/objects pushed to DSA since commit
> 2ea7a679ca2abd251c1ec03f20508619707e1749 ("net: dsa: Don't add vlans
> when vlan filtering is disabled") so I am not sure how you got into that
> situation because prior to pushing a VLAN object, the port must be part
> of a bridge, so the steps typically look like:
> 
> - port_bridge_join which assigns dp->bridge_dev
> - port_vlan_add
> 
> Does your 4.19.23 kernel somehow change how VLAN objects are pushed down
> the switch driver?
> 
>> [  352.057128] bridge_name: port 1(lan0.5) entered blocking state
>> [  352.063065] bridge_name: port 1(lan0.5) entered disabled state
>> [  352.069181] device lan0.5 entered promiscuous mode
>> [  352.074018] device lan0 entered promiscuous mode
>> [  352.078906] Unable to handle kernel NULL pointer dereference at virtual address 00000558
>> ...
>> [  352.493085] [<bf0fde88>] (br_vlan_enabled [bridge]) from [<bf12c234>] (dsa_port_vlan_add+0x60/0xbc [dsa_core])
>> [  352.503050] [<bf12c234>] (dsa_port_vlan_add [dsa_core]) from [<bf12cb64>] (dsa_slave_port_obj_add+0x4c/0x50 [dsa_core])
>> [  352.513776] [<bf12cb64>] (dsa_slave_port_obj_add [dsa_core]) from [<c0b4e2d4>] (__switchdev_port_obj_add+0x50/0xc4)
>> [  352.524138] [<c0b4e2d4>] (__switchdev_port_obj_add) from [<c0b4e324>] (__switchdev_port_obj_add+0xa0/0xc4)
>> [  352.533721] [<c0b4e324>] (__switchdev_port_obj_add) from [<c0b4e3a8>] (switchdev_port_obj_add_now+0x60/0x130)
>> [  352.543562] [<c0b4e3a8>] (switchdev_port_obj_add_now) from [<c0b4e7e4>] (switchdev_port_obj_add+0x44/0x190)
>> [  352.553284] [<c0b4e7e4>] (switchdev_port_obj_add) from [<bf1013d0>] (br_switchdev_port_vlan_add+0x60/0x7c [bridge])
>> [  352.563733] [<bf1013d0>] (br_switchdev_port_vlan_add [bridge]) from [<bf0ff250>] (__vlan_add+0xb0/0x620 [bridge])
>> [  352.574007] [<bf0ff250>] (__vlan_add [bridge]) from [<bf0ffd04>] (nbp_vlan_add+0xc4/0x150 [bridge])
>> [  352.583073] [<bf0ffd04>] (nbp_vlan_add [bridge]) from [<bf0ffec4>] (nbp_vlan_init+0x134/0x164 [bridge])
>> [  352.592482] [<bf0ffec4>] (nbp_vlan_init [bridge]) from [<bf0edd4c>] (br_add_if+0x40c/0x5fc [bridge])
>> [  352.601632] [<bf0edd4c>] (br_add_if [bridge]) from [<bf0eeb14>] (add_del_if+0x6c/0x80 [bridge])
>> [  352.610351] [<bf0eeb14>] (add_del_if [bridge]) from [<bf0ef5b0>] (br_dev_ioctl+0x7c/0x9c [bridge])
>> [  352.619290] [<bf0ef5b0>] (br_dev_ioctl [bridge]) from [<c09583d4>] (dev_ifsioc+0x184/0x324)
>> [  352.627582] [<c09583d4>] (dev_ifsioc) from [<c09589e8>] (dev_ioctl+0x32c/0x5cc)
>> [  352.634837] [<c09589e8>] (dev_ioctl) from [<c090913c>] (sock_ioctl+0x3bc/0x580)
>>
>>
>> since my 4.19.23 kernel is modified a bit i tried with 4.19.10 without my net modifications and it is still reproducable with steps above (create a vlan on dsa-user-port and then use it in a bridge)
>>
>> i fixed it with these changes:

Your fix is undoing the commit from Andrew I just referenced, so it is
definitively not the right fix because it will push VLAN objects down to
a non-VLAN aware bridge, not that this is really a problem, but it
should not be happening anyway.

The problem appears to be the following though: you are enslaving a VLAN
device, which does not have switchdev_ops, so we recurse into the lower
device, which is the DSA network device, which does have switchdev_ops
defined. Once we are there we check the orig_dev against being a bridge
master network device, but we are not checking that it's a VLAN device
so we end-up assuming it is a DSA network device, we de-reference
garbage by checking br_vlan_enabled(dp->bridge_dev) because there is
simply no such data structure associated with the VLAN device.

The attached patch should help.

This is no longer a problem in newer kernels because the switchdev
operations use a notifier which checks the target network device to be DSA.
-- 
Florian

View attachment "0001-net-dsa-Prevent-oops-while-enslaving-non-DSA-devices.patch" of type "text/plain" (2684 bytes)

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